Vol. 8, No. 1, 75-92, 2009
Mapping Leaf Area Index over semi-desert and steppe biomes in Kazakhstan using satellite imagery and ground measurements|
Pavel Propastin and Martin Kappas
Maps of peak seasonal leaf area index (LAI)
were produced using the Normalised Difference Vegetation Index (NDVI) from
SPOT VEGETATION (VEG) satellite at 1 km resolution
over a large region in the semi-arid zone of Kazakhstan. Ground measurements of
LAI were acquired using indirect and
direct techniques across a 150·150 km2 large region. A Landsat Enhanced Thematic
Mapper (ETM+) scene at 30 m spatial resolution was used to locate ground sites and to
facilitate spatial scaling to 1 km pixels. A
high-resolution LAI map retrieved
from the Landsat ETM+ data was
aggregated to 1 km resolution and afterwards used as reference data.
The methods tested for transfer function between ETM+ LAI and SPOT-VEG were ordinary least
squares (OLS) regression, non-linear regression, and reduced major axis
(RMA) regression. In this paper, final maps of peak season LAI at a 1 km resolution
are presented after an assessment of their accuracy using the aggregated ETM+ LAI scene.
The most appropriate results were attained by RMA. Advantages and shortages of the used
regression approaches were analysed and discussed. Errors were
mostly caused by uncertainties in co-registration of Landsat
ETM+ and SPOT-VEG images as it was demonstrated by a pixel degradation experiment.
The methodology presented in this paper can serve as a basis for generation of
medium- and coarse-resolution LAI
satellite products for wide areas of Central Asia and Kazakhstan. The study exposed a
general transferability of the developed model
for LAI estimations at coarser
scales. The 1000 m SPOT-VEG model has proved to be fully suitable for
utilising with the SPOT-VEG data with resolution of 2 km.
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Submitted: 04 Nov 2008
Revised: 05 May 2009
Accepted: 05 May 2009
Published: 29 Jun 2009
Responsible editor: Zbigniew Bochenek
Propastin P & M Kappas, 2009.
Mapping Leaf Area Index over semi-desert and steppe biomes in Kazakhstan using satellite imagery and ground measurements.
EARSeL eProceedings, 8(1): 75-92